Modulation system



April 1940. H. TISCHNER 2,196,163

MODULATION SYSTEM Filed Sept. 15, 1936 sausage; v aura/er ENERGY 14 3.

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OSCIUATORY ENERGY INVENTOR v HORST TISCHNER BY'\- 11 arm ATTORNEY .Patented Ap 2 1940 i r Y 2,196,163

UNITED STATES PATENT 1. OFFICE MODULATION SYSTEM 'Horst Tischner, Berlin, Germany, assignor to Allgemeine Elektricitats-Gesellschaft, Berlin, Germany, a corporation of Germany Application September 15, 1936, Serial No. 100,846

In Germany September 27, 1935 2 Claims. (01. Mil-171.5)

The present application concerns a novel cirmanufacturing reasons fail to be perfectly symcuit organization adapted to insure symmetric metric. The balancing condensers C and C have conditions in push-pull modulators and comthe purpose to effect a balance of the two bridge prises reactances and non-reactive resistances arms in such fashion that the bridge points a 5 arranged to balance the grid potentials of both and b are at the same potential, 1. e., earth 5 tubes both as regards amplitude and phase. potential; this means that no alternating current One essential desideratum of all push-pul1cirwill flow in the connection between the filament cuit schemes is that they should be designed with (point 17) and the transformer midpoint or center perfect symmetry. In modulator circuit artap at a (see Figure 1). In order that the ohmic l0 rangements in which the carrier wave is supresistances Rgl and Rg2 may be matched to the pressed, symmetry of construction is of vital imbridge relation, the ohm resistances of the inportance. Serious difliculties in this regard re-, ductances L1 and L'1 which are not indicated in side in and are occasioned by inherent distributed the figures, must be chosen accordingly. capacitances within the windings of the trans- Fundamentally, two kinds of capacitive balance formers. For in order toreduce leakage of transare feasible. Either the balance condensers C 5 formers, the primary and the secondary windings and C are connected in parallel relation to the have been sub-divided, and these sub-divisions secondary windings L1 and L'1 of the audio freare alternately placed on the core. This special quency input transformer Tn as shown in Figure construction of the transformers has the draw- 1 or else in parallel relation to the secondary back that these sub-divisions of the coils present windings L2 and L'2 of the radio frequency input 20 different capacities to ground, and this introtransformer Tr2 as shown in Figure 3. Which of duces dissymmetry into the whole circuit scheme. the two would be more suitable and preferable is Another disturbing element and fact is that the a question that can be decided only on the merits resistances and the capacities of the grid-filaof each individual case.

ment path in tubes manufactured on a large I claim: 25 scale will never be perfectly alike inside one and 1. In a modulator circuit, a source of carrierthe same type, and this likewise is liable to disfrequency oscillations, a transformer having a turb or vitiate the symmetry of construction. primary winding fed with energy from said source The object of this invention-is to provide a and two secondary windings, a push-pull amplimethod of and means for making the two circuits fier having a pair of discharge tubes, each tube 30 of a push-pull modulator circuit scheme perfectly having a plurality of electrodes including a conalike. The idea which underlies the invention trol grid, input circuits each connected'to one of will be understood most clearly and easily by said control grids and including one of said reference to the annexed drawing wherein: secondary windings respectively, means for feed- 5 Figure 1 illustrates a balanced push-pull ciring said carrier frequency energy from said sec- 5 cuit arranged in accordance with my invention; ondary windings co-phasally to said input cir- Figure 2 shows the circuit of Figure 1 in bridge cults, a source of modulating potentials, means form; while for feeding said modulating potentials contra- Figure 3 is a modification of Figure l. phasally to said input circuits, a separate adjust- 40 Figure 1 is an exemplified embodiment of a able resistorin series with each secondary wind- 40 push-pull modulator circuit organization. The ing for balancing the potentials respectively imfundamental circuit diagram is shown in Figure pressed on-said input circuits, and means includ- 2. It will be clearly seen that what is here ining an independently adjustable capacitance in volved is a bridge-type circuit arrangement. C shunt with each secondary for balancing the 4,5 and C are the balancing condensers the operaphases between the respective modulating poten- 5 I tion of which is to be discussed further below. tials as impressed upon said control grids. Ce and 0's stand for the ground capacitances of 2. In a modulating system, a push-pull arwinding L1 and L'1 of the audio frequency input rangement of two discharge tubes each having a transformer Tn. Land L's stand for the secplurality of electrodes including a cathode and a ondary windings of the radio frequency input control grid, an input circuit for each tube con- 5 transformer Trz. The primary winding of this nected between its cathode and control grid, a transformer represents the radio frequency transformer having a primary winding and two source B. Cgl, C z and Rgl, RgZ, respectively de-' secondary windings disposed in substantially note the grid-filament capacity and the grid-filabalanced relation to the primary, one secondary ment resistance of tube V1 and V: which for winding being included in each said input cir- 55 cuit, means including a source of carrier Waves connected to said primary for applying energy across said secondary windings and thence cophasally to the respective control grids of said tubes, means including a source of modulating frequency waves connected to said secondary windings for applying modulating energy contraphasally to said control grids, means including two independently adjustable capacitors, one in shunt with each secondary winding, for obtaining a compensating reactive balance between said input circuits with respect to said modulating frequency waves, and means including two independently adjustable resistors, each in series with one of said secondary windings respectively, for obtaining a compensating ohmic balance between said input circuits.

HORST TISCI'INER. 

